1. Field of the Invention
The present invention relates to a terminal for reproducing digital contents and a method for transmitting/receiving digital contents; and, more particularly, to a digital contents reproducing terminal and a digital contents transmission/reception method that can prevent digital contents from being illegally copied and distributed.
2. Description of Related Art
Digital contents are data or information obtained by producing and processing code, text, speech, sound, image and video in a digital method. Digital contents include audio-visual contents, such as dramas and movies, and video games. The forms and range of digital contents are expanding constantly.
Since digital contents can be copied easily and quickly and the copy versions maintain the same quality as the original versions, they can be readily distributed through wired/wireless electrical communication networks. Accordingly, distribution of such digital contents through unlawful distribution channels and illegal copying and distribution of the digital contents emerge as problems.
These problems call for Digital Rights Management (DRM) technology, which prevents digital contents from being unlawfully copied and distributed by distributing the digital contents through user authentication and charging processes.
In the initial days, however, the DRM technology obstructs the illegal copy of digital contents on a single device basis. Thus, although a user receives a digital content through a lawful distribution channel, only the device which received the digital content are allowed to use the digital content. In other words, the user cannot use the digital content in another device of his. This infringes on the lawful personal use of the user.
For example, when a user pays a predetermined amount of money and downloads a digital content into his personal computer (PC), he is not allowed to copy and transmit the digital content to his Portable Multimedia Player (PMP). Although the user has a lawful right of using the digital content, he cannot freely use the digital content within the scope the user can use it personally, which will be referred to as a personal use scope hereafter, and this is a problem.
To protect the right of a user personally using a digital content, conventional technology called domain technology was suggested. Domain technology allows a user to register a plurality of devices that belong to the personal use scope of the user, which are terminals owned by the user, in a domain and share a digital content among the registered terminals. Hereafter, the conventional domain technology will be described with reference to the accompanying drawings.
FIG. 1 illustrates a typical domain technology. Particularly, the drawing describes whether a digital content can be transmitted between terminals according to a personal use scope.
As illustrated, a plurality of terminals 100, 110, 120, and 130 may be included in a personal use scope (A) of a user, and some 100, 110 and 120 of them may be registered as a group, i.e., a domain B, based on the domain technology.
The domain technology has two ways of registering devices. First, terminals 100, 110 and 120 that belong to a personal use scope A are registered as a group in a domain registration and management server and the domain registration and management server assigns a domain to the group. Second, a master function is given to any one terminal 100, which will be referred to as a master terminal, among the multiple terminals that belong to a personal use scope A and the master terminal 100 registers the other terminals 110 and 120 of the personal use scope A.
The terminals 100, 110 and 120 registered in the domain
B share a domain key. A domain key refers to an encryption key shared by only the terminals 100, 110 and 120 that belong to the domain B. With the domain key, the terminals 100, 110 and 120 can share the digital content.
FIG. 2 illustrates how data are processed in a transmission terminal when a digital content is transmitted between terminals registered in a domain. Hereafter, it is assumed that a first terminal 100 transmits a digital content to a second terminal 110.
As illustrated, the first terminal 100 scrambles the digital content by using a scrambling key. Also, the first terminal 100 encrypts the scrambling key by using a domain key to thereby generate personal-use authentication information. The personal-use authentication information is information for descrambling the scrambled digital content, and only a terminal with the domain key can use the digital content by using the personal-use authentication information.
The first terminal 100 transmits the scrambled digital content and the personal-use authentication information to the second terminal 110.
The second terminal 110 decrypts the encrypted scrambling key from the personal-use authentication information by using the domain key, and descrambles the scrambled digital content by using the scrambling key. In this way, the digital content is decrypted.
As described above, as the scrambled digital content and the personal-use authentication information are transmitted together when the digital content is requested to be transmitted, it is possible to use the digital content in terminals registered in the domain B, which are allowed to use the digital content.
The conventional domain technology, however, allows only the terminals 100, 110 and 120 registered in the domain B to share the digital content. In other words, a fourth terminal 130, which is within the personal use scope of the user but not registered in the domain B, cannot share the digital content.
For example, a terminal which is not yet registered in the domain B or cannot be registered in the domain B, or a terminal which is designed for one-time use and not appropriate for registration in the domain B cannot use the digital content, even though the terminal is still within the personal use scope A of the user.
In short, the conventional domain technology has a problem of restricting the personal use scope A of the user because it allows the use of the digital content based on whether a terminal is registered in the domain B. Therefore, it is required to develop a technology that can secure the personal use scope of a user regardless of whether a terminal is registered in the domain or not.